Process of treating natural phosphate-rock.



F. K. HOOVER & A. J. MASON.

PROCESS OF TREATING NATURAL PHOSPHATE ROCK. APPLICATION FILED JUNE 9,1911.

Patented Feb. 16, 1915.

FRANK K. HOOVER AND ARTHUR J. MASON, OF CHICAGO, ILLINOIS.

' PROCESS OF TREATING NATURAL PHOSPHATE-ROCK.

raaaera,

Specification of Letters Patent.

Patented lFeb. to, 1915.

Application filed June 9, 1911. Serial No. 632,234.

T all whom it may concern:

.Be it known that we, FRANK K. Hoover: and ARTHUR J. MASON, citizens ofthe United States, residing at Chicago, in the county of Cook and Stateof Illinois, have invented a new and Improved Process of TreatingNatural Phosphate-Rock, of which the following is a specification.

This invention relates to a new and improved method of treating naturalphosphate rock which is extensively used at the present time as afertilizing agent. Phosphate rock is a natural mineral deposit occurringto a considerable extent in Tennessee and other parts of the country,being usually found at a depth of from five to thirty feet below thesurface of the ground and existing in strata of varying thicknessesbeneath an over-lying stratum of clay. The phosphate or brown rockdeposit in its natural state is found .in pieces varying from rocks ofconsiderable size down to fine powder. The larger pieces arecomparatively pure, and the present somewhat wasteful method consists inutilizing principally the larger pieces and roughly washing them toobtain the desired percentage of purity, discarding the finer materialwhich contains a considerably greater percentage of clay and otherforeign matter. proportion of the total material existing in the fineform is, in many localities, a very considerable percentage of thewhole, it is highly desirable from the viewpoint of economy to save suchfine material; but to increase its commercial value it is necessary topurify it of the contained clay; and it is the chief purpose and objectof the present invention to efiect such a cleaning or purification ofthe entire body of material, including the finer part, so as to bringthe whole up to the desired or required standard of purity. We havefound from extensive work on a considerable variety of the brown rock ofTennessee that the portion represented by the finer particles, that'is,those smaller than one-twentieth of an inch in diameter, if properlywashed, will retain nearly the same percentage of phosphate of lime asthe large pieces, and our present process consists in a method oftreament whereby the whole deposit consisting of the so-called phosphatesand as well as the large lumps and rocks may be caused to yield a Asthe I resulting product which will grade substantially the same as whenthe large pieces only are selected.

Our process, as to its main or essential steps or operations, consistsin, first, the rubbing and grinding of the material on itself to bringall the clay to a solvent condition; second, diluting the samethoroughly with sufficient water; and, third, the separating of the rockfrom the dirty water. A

preliminary operation of grinding or crushwherein we have illustrated,somewhat diagramatically, a group of devices well adapted for thecarrying out of the several steps of the treatment; although it is to beunderstood that the performance of the several acts and operationsinvolved in the process is by no means dependent upon the particulardevices herein illustrated for this purpose.

The material as received from the mine consists of a mass generally verywet and composed of pieces ranging in'size from that of a mans head downto extremely fine material such as impalpable powder, containingintermixed therewith a considerable amount of clay, iron andsand,chiefly clay. For convenience we first provide a receiving hopper Afor this rock preferably of considerable capacity for the purpose ofguarding against the intermittent operations at the mine due to weatherconditions and other causes. At the lower portion of said hopper weprovide a rotary feed gate B, preferably of the form and type disclosedin our Patent No. 753,076, granted Feb. 23, 1904-. The rock is emittedfrom the receiving hopper in a continuous and regulated stream and ispassed through one or more pairs of crushing rolls, two being hereinindicated at C and D, the rolls of the two pairs be (ing spaced atdifferent distances apart, the

upper rolls being set about four inches apart and the lower rolls abouta half inch apart, so as to insure the crushing 'of both the larger andsmaller pieces and effecting the reduction of the wholeto the desiredsize for treatment. From the rolls the material falls into a devicewhich we have denominated a m'ulcher shown at E. We have found intreating this phosphate rock to cleanse the same-of the associated claythat something more is necessary than the customary tumbling in thepresence of water. We have demonstarted that if this same material isfirst subjected to a' thorough rubbing action, such as a person subjectshis hands to in washing them with soap, in the presence of justsufficient water to soften and render plastic the mass, it is thenbrought to acondition highly favorable for the next step in the processof its cleansing.

A microscopic examination of phosphate rock as now maiketed reveals thefact that a large proportion consists of grains very much like ordinarybuilding sand, each grain more or less coated with clay carrying someiron. If these grains be vigorously rubbed against each other in thepresence of a small amount of water, a scouring effect is had, so thaton-further rinsing with more water they will appear clean and free fromthis coating of clay and iron. The object of this mulcher, therefore, isto subject the mass of material to this rubbing andscouring .action.This device, which forms the subject matter of another application filedby us June 9, 1911, Serial No. 632,235, consists, generally stated, of anumber of superimposed ring-shaped holders e and e, alternate holdersbeing mounted to rotate and the intermediate holders being eitherstationary or rotating in the opposite direction. As-the material feedsdown between these holders, theportions contained in adjacent holdersare rubbed against each other,'and

as the material is constantly and slowly passing through the holders, avery thorough and intimate rubbing of the particles -of the entire massupon and against each other is obtained. We find that this rubbing andscouring action is best obtained when the material has about aconsistency a little stiffer than that of mortar usually employed inplastering buildings, and for this purpose we add a small temperingstream of water through a pipe-F which is controlled in a manner similarto that employed in brick making in the preliminary preparation of theday. From between the rings e and e the material'falls upon a rotatingplate E, from the periphery of which it is uniformly withdrawn by-'astationary plow indicated at E ,After the material is passed throughthis mulcher, its appearance and behavior i indicate a marked change inits condition,

and it is obvious from ins ection that all the clay has been softene andloosened from the particles of phosphate rock. this time the materialresembles a pulpy mass, the majority of the particles of which arephosphate rock of varying sizes.

The next step in the operation consists in bringing the clay into acondition of complete suspension in water. For this purpose the materialdischarged from the mnlcher is passed through a chute Ginto what we terma dasher H, which consists of a rotatable cylinder set slightly out ofthe horizontal and having set around its interior a series oflongitudinal buckets h, and to which water is continuously supplied, asthrough a perforated pipe h lying in the upper part of the cylinder. Therevolution of the dasher causes the material and water intermixedtherewith to be lifted by the buckets h and frequently drepped'uponitself. In this way the added waterthoroughly mixes with the clay, andon emission from the lower end of the dasher the material is in asuitable condition to begin the proce% of separation,

containing at this time about one and oneing an opening at. its bottomsealed by a ball valve 3' and provided at its top with a seriesofchannels 7' laid across the same for 'the purpose of diffusing theover-flow over substantially the whole area of the cone and thusproducing a uniform upward current, the cone J being normally filled andbrimming over. This over-flow contains, of course, mud in suspension,and with it some of the -finer particles of phosphate rock. The bulk ofthe phosphate rock, however, piles up at the bottom of the cone, and is,from time to time, discharged by opening the valve'j, and delivered,accompanied by about an equal quantity of muddy water, into anunderlying tank K which constitutes the lower part of the separator. Thepurpose of this latter device is to thoroughly expel with clear waterthe mud that fails to pass off in the overflow from the cone .l andrinse the solid particles of phosphate rock. .To facilitate thisoperation we provide within the tank K a zigzag annular passage formedbetween outer and inner corrugated partitions Z, Z. clean water being,let into the lower portion of the tank K a i m wardly through a zigzagannular passage to the top of the tank K, and in so doing meets andintercepts with a rinsing action the descending particles of phosphaterock, the latter falling to the bottom of the tank K, and the mud risingwith the upflowing stream of water. To render the upward flow in thetank K as uniform as possible and efiect its diffusion over the wholearea of the tank We likewise provide at the top of mud and otherimpurities passln through the overflow trough m By means of the latter anumber of channels similar to the channels 7' of the upper separator,through which the rising volume of water with the balance of the mud andsome finer particles of phosphate rock in suspension therein flows,together with the overflow from cone J into a trough L, whence theentire overflow passes into a further separator operating upon thewater-fall or cascade principle and consisting essentially of a tank Mcontaining a number of vertical transverse partitions m of graduallydecreasing height and forming a row of compartments having a graduallystepped relation,'thereby producing a series of minute cascadesdelivering in succession to each other from the front to the rear end ofthe tank, the fine particles of the heavier phosphate rock settling tothe bottoms of the several successive compartments, and the lighterpargiclefis of this auxiliary separator, thefinest particles ofphosphate rock, running froin 1/80 to 1/500 of an inch in diameter, andrepresented generally by the impalpable powder constituent, and whichwould be otherwise wasted in the overflow from the main separator, arerecovered. Returning to the main separator, the. bulk of the phosphaterock falls to the bottom of the tank K and is from time to timewithdrawn through a cen-. tral hole in said bottom by opening a ballvalve 70 the material falling through a chute N into-a skip-car 0,whence it is conveyed through delivery troughs P into a series ofdraining-tanks Q. We prefer to employ two or more such draining tankswith delivery to and from each in succession in order to give time forthe contained water to drain. Each tank has at its bottom afiltering-bed q composed of coarse material, such as coarse phosphaterock,

crushed limestone, cinder, or any suitable material, through which andthe bottom of the tank is set a delivery spout q. The water is drainedofi through a drain-pipe g and in order to accelerate the draining weintroduce into each drain pipe a steam ejector jet or nozzle indicatedat g When the drainage tank has been filled with the washed phosphaterock and given time for drainage, and is ready for the drying operation,we find that it has assumed a condition so water-packed that it will notflow even when a very large opening as large as three feet in diameteris made in the floor of the tank or receptacle. In order to cause it toflow out of the tank, we first bore ahole through the exit opening gfrom below upwardly to' the full height of the material in the tank,using for this purpose an earthboring augerzof suflicient size (actuallyabout nine inches in diameter). The material is then shoveled from thetop into this hole and passes thence into an underlying feed-hopper R atthe bottom which regulates the supply of material to the drying devices.While it is true that this material packs in the manner above described,yet after it has been drained and once loosened it remains in the loosecondition, like ordinary building sand, and flows freely in any desiredmanner. The expeditious removal of the drained phosphate rock from thesedraining tanks has heretofore presented quite a serious problem; butoperating in the manner above described the material is easily removedand the capacity of a single operator becomes very great, as high as tentons per hour. y

We find that if a tank be filled with the material described, Within anhour or two, by means of a steam-ejector, it may be brought to acondition wherein the water is only about seventeen per cent. of theweight of the Whole, whereas in the customary method of treatingphosphate rock this material passes to the drying apparatus containingnot less than twenty-five per cent. of water. When it is borne in mindthat a great preponderance of the heat required to dry phosphate rock isexpended in merely evaporating the contained water, it will be seen thatthe preliminary draining which We employ effects a substantial reductionin the fuel necessar to effect the final and artificial drying. on thematerial in each drain-tank is ready for drying by artificial heat, thevalve 1* at the lower end of the deli-very nozzle 9 is opened, and thematerial ejected in the manner above de-- scribed flows out into thehopper R and is delivered thence by the feed-rollerrthrough a chute S tothe drier T. This latter, which forms the subject matter of anotherapplication filed by us June 9, 1911, Serial No. 632,239, consistssubstantially of a rotary drum t made up of a plurality of endwiseconnected cast-iron sections, and slung by wire ropes t from pulleys ton an overhead rotating shaft t said drum being set within an ordinary.furnace chamber 15. The drum is suspended at a slight angle and isformed interiorly with a number of integral longitudinal concaves orscallops which pick up and tumble the material upon itself, and the drumis provided near its discharge end with an annular row of ppenings whichserve the double function of delivering the combustion through theinterior, as well as around the exterior, of the drum; such gases.

and products of combustion passing off through a casing W underlying thefeed devices and a flue X to the chimney. As the drum t of the drierrevolves it causes the material therein to be constantly alive andmoving, and therefore in a favorable condition to release the steamconstantly being generated. The material is thus subject to direct andintimate contact with the hot gases and likewise to direct contact withthe hot metal which receives its heat largely from the externalexposure.

In order to clearly describe a practical mode of treatment of phosphaterock beginning with the material as it comes from the mine or ore-bedand ending with the clean and dried material ready for the market, wehave described all of the various steps or operations which Wepreferably employ, including those for recovering the finest particleswhich have heretofore been Wasted. It should be understood, however,that not all of these operations are indispensable tothe obtainment of asatisfactory product in accordance with our present invention; the mainand distinguishing acts or operations residing in the loosening of therock from the adhering clay, the bringing of the latter thoroughly intosuspension in water, and

the separation of the rock from the loosened and suspended clay; theother described operations being ancillary thereto and preferablycarried out to secure the most satisfactory results in the character ofthe prodnot and the economy and efficiency of theprocess.

We clalm I 1. The method of removing foreign matter from a naturalmineral deposit such as.

phosphate rock, which consists in subjecting the phosphate ore to amutual attrition of the components thereof in the presence of suflicientwater only to form a plastic mass, thereafter-subjecting the material toa tumbling action in the presence of an added quantity of Water tosuspend all the mateterial to a mutual rubbing movement to,

effect an attrition.of said foreign matter and the consequent formationof a plastic mass consisting of a mixture of the said water, mineral andtriturated foreign matter, then adding to said mixture a sullicientquantity of water to suspend all of the material in water, and finallyremoving the clean ore by gravity while subject to cleaning currents ofwater.

FRANK K. HOOVER. ARTHUR J. MASON. W itnesses SAMUEL N. POND, C. A.KnNYoN.

